That's actually pretty depressing. There are some obviously jokey ones such as David Prowse (Darth Vader) playing Cuddy and Danny DeVito as Carrot, but some of them I think were actually serious.
Someone seems to be a Jim Carrey fan as he's mentioned for almost all the roles.
Oddly enough Sir David Jason doesn't appear as much as one might imagine.
In my experience casting threads often cause arguements on message boards.